This is another nice decompression tool does RAR among others>>>Extractnow

EDIT:
If you install 7-Zip just right click on the file and select extract here
For extractnow double click and hit the extract button
Then you should have the file thats within the archive ready for whatever patching you need to do

That I can't help you with. U might wanna try the name of the site you downloaded it from e.g. say you got it from www.gbatemp.net then try gbatemp.net as the pass. The password will have been posted somewhere u just gotta find it